Polyurethane Adhesive with Semi-Crystalline Polyesters
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Solution Overview
Problem
Polyurethane adhesives lack high fixture strength and green strength, which are crucial for handling and curing processes, while maintaining other advantageous properties like open time and tensile strength.
Innovation Solution
A polyurethane adhesive is formulated using a mixture of semi-crystalline and highly crystalline polyesters, with the highly crystalline polyester having a higher melting point than the semi-crystalline polyester, in specific weight ratios to enhance green strength without compromising open time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high molecular weight acrylates are employed to increase green strength, then green strength is improved, but jettability deteriorates
Solution Approach 1:
The invention changes the chemical composition parameters by introducing highly crystalline polyester with specific melting point (higher than semi-crystalline polyester) and controlling its content (0.1-10 wt%, preferably 0.5-5 wt%). This parameter change achieves improved green strength through enhanced crystalline structure formation while maintaining proper flow characteristics for jettability during application.
Solution Approach 2:
The invention creates a composite adhesive system combining semi-crystalline polyester and highly crystalline polyester in specific proportions. This composite approach allows the semi-crystalline polyester to provide base adhesive properties and open time, while the highly crystalline polyester contributes to enhanced green strength through its superior crystalline structure, achieving both goals simultaneously without the drawbacks of high molecular weight acrylates.
2Strength
If the amount of highly crystalline polyester is increased to improve green strength, then green strength is improved, but open time deteriorates
Solution Approach 1:
The invention optimizes the melting point parameter of the highly crystalline polyester, selecting materials with melting points higher than semi-crystalline polyester (which typically melts at 50-100°C). This melting point differentiation ensures that the highly crystalline polyester remains solid during application but provides structural support during curing, improving green strength without interfering with the open time required for proper bonding.
Solution Approach 2:
The invention applies local quality differentiation by having semi-crystalline polyester provide the amorphous matrix that maintains open time and flexibility, while highly crystalline polyester provides localized crystalline domains that enhance green strength. This spatial and functional differentiation allows both properties to coexist without mutual interference.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The adhesive exhibits improved green strength and maintains the required open time, ensuring the adhesive bond is strong enough for handling before full cure, while avoiding negative impacts on application properties.
Implementation Method 1
the melting point of the highly crystalline polyester being higher than the melting point of the semi-crystalline polyester
Implementation Method 2
Crystallization of polymers is a process associated with partial alignment of their molecular chains. In the course of the present invention, semi-crystalline polyester refers to a polyester comprising crystalline and amorphous areas. Highly crystalline polyester refers to a polyester having a high degree of crystallinity
Data Source
AI summary
The present invention refers to polyurethane adhesives with semi-crystalline and highly crystalline polyesters, a method for the production of the same as well as the use of the polyurethane adhesive in the production of electronic devices.